From the art, several types of circuit carriers are known. A circuit carrier consists basically of a substrate of a dielectric material, which is provided with electrically conductive tracks, to connect electronic components. One type of circuit carrier are so-called MIDs (MID=Molded Interconnect Device), which are three-dimensional molded circuit carriers. MIDs are injection three-dimensional molded parts, with integrated circuit tracks. MIDs are molded from thermoplastic material as e.g. polypropylene (PP), polycarbonate (PC), polyamide (PA). In the art, there are several manufacturing processes known to produce MIDs. One method is e.g. the so-called hot embossing. In this method, first the dielectric substrate is molded from a thermoplastic material. After that, a copper foil is arranged on the surface of the dielectric substrate and substrate and copper foil are arranged in a press. In the next step, a heated dye with an engraved circuit pattern for embossing is pressed onto the copper foil. After that, the excess foil is removed from the thermoplastic substrate and the plated MID is ready for application.
Printed circuit boards are another very common type of circuit carrier. Printed circuit boards are widely used in the industry to mechanically support and electrically connect electronic components. PCBs consist of a dielectric substrate, the board, which is provided with conductive pathways or tracks, which are usually cut from copper sheets and are laminated onto the board. The substrates of PCBs are usually made from fiber-reinforced epoxy resins. Epoxy resins have excellent mechanical properties with regard to hardness and they provides good chemical and heat resistance. In printed circuit boards, the application of contact pins to provide an electrical connection between electronic components is very common. For the reception of such contact pins, the printed circuit boards are provided with throughholes, whereby the inner surface of the throughholes is provided with an electrically conductive coating. The electrically conductive coating of the throughhole is in contact with one or more of the conductive tracks provided on the board. The contact pins are then inserted into the throughholes and are subsequently soldered to fasten the contact pins with the board and to provide an electric connection. In the industry, the large-scale soldering of PCBs is usually done by means of wave-soldering, whereby the contact pins are inserted into the PCB and the PCB is then passed with its underside over a standing wave of solder. The solder wets the metallic areas of the board, creating a reliable mechanical and electrical connection. In the art, it is further known to mount contact pins by means of press-fit into a PCB. This is possible since the epoxy resins used for PCBs are very hard, so that the press-fit of a metallic contact pin does not widen or enlarge the hole provided in the PCB. However, with such press-fits, very tight tolerances have to be observed.
To avoid the very high production tolerances necessary for a press-fit, i.e. for the contact pin and the corresponding hole in the PCB, contact pins with spring-like compressible profiles were developed. If such a pin is pressed into a corresponding hole in a PCB, the compressible or spring-like section of the pin is deformed and may be fitted into the hole.
The present invention relates to a contact pin for providing electrical connection between electronic devices, which pin is adapted to be installed in the hole of a circuit carrier, in particular of a circuit carrier made of a thermoplastic material, such as MID.
In particular, it is an object of the invention to provide a cost-efficient, mechanically stable contact pin for electrical connection between electronic devices. It may be a further object of the invention to provide a contact pin, which provides a solder-less electrical connection and which is adapted to be inserted into a hole of a circuit carrier, in particular an MID. It may be still a further object of the invention to provide a contact pin, which may be used with thermoplastic materials, and which may in particular be fastened in holes provided in thermoplastic substrates without widening or destroying the related hole and/or which may compensate for production tolerances or deformations commonly occurring in the thermoplastic substrate due to mechanical or thermal stress. It may be a further object to provide a contact pin, which may be fastened in thermoplastic material without getting loose, when the thermoplastic material is subjected to creep over time or under the influence of temperature as it is common for such thermoplastic materials. It may be a further object of the invention to provide an improved system for connecting electronic devices, wherein contact pins can be mounted into holes provided in the dielectric substrate of a circuit carrier.
It is another object of the invention to provide a system for connecting electronic devices comprising contact pins, which are inserted into holes in circuit carriers. At least one of these and other objects, which will derive from the following description, are solved by the present invention.